Specialized machines are known to the art which are designed to solder electronic component leads to the conductors of printed circuit boards. However, the prior art machines, insofar as applicants are aware, have all been designed to handle only one lead configuration. Such prior art machines are not useful, therefore, for soldering purposes in cases where a variety of different types and sizes of electronic components are used in conjunction with a single printed circuit board. It has been found in the past, under the latter conditions, that the only practical technique is to hand solder the component leads on an individual basis, which is expensive and time consuming.
The prior art mechanisms, moreover, have a tendency to produce solder joints which contain high residual stresses, because the prior art machines do not include any means for relieving stresses during the individual soldering operations. The lack of a stress relieving means in the prior art machines creates solder joints which are prone to failure during temperature cycling and subsequent usage in the field.
The mechanism of the present invention, on the other hand, is designed to be capable of soldering on a simultaneous basis, the multiple leads of a wide variety of electronic components of different shapes and sizes. This feature permits the mechanism of the invention to be used in conjunction with assemblies in which electronic components of many sizes and having many different numbers of leads are to be soldered to the conductors of a particular printed circuit board.
Unlike the prior art machinery, the mechanism of the present invention can be moved from component to component, and can be adapted to solder the leads of each individual component on a simultaneous basis to the printed circuit conductors on the circuit board, regardless of the size of the component or of the number of leads, and without any need for time consuming changes in the basic set-up of the soldering mechanism.
Moreover, the soldering mechanism to be described incorporates a stress relieving cycle, by which the leads of the various electronic components are soldered to the printed circuit conductors on the circuit board under an environment of reduced stress, so that as the solder hardens at each joint, the stress within the soldered joint is minimized. In this way, the soldered joints made by the mechanism of the invention are not prone to failure during subsequent temperature cycling and field usage.